Doug Selsam's Sky Serpent uses an array of small rotors to catch more wind for less money
By Kalee Thompson Posted 05.13.2008 at 12:30 pm 19 Comments

WIND WIZARD Doug Selsam sits beneath a prototype 25-rotor turbine that can produce three kilowatts of power. The other end is held aloft by a balloon. John B. Carnett

Sky Serpent
Cost to Develop: $250,000
Time: 9 years
Prototype | | | | | Product
Today’s largest wind farms are the size of small towns, made up of turbines 30 stories tall with blades the size of 747 wings. Those behemoths produce a great deal of power, but manufacturing, transporting, and installing them is both expensive and difficult, and back orders are common as the industry grows by more than 40 percent a year. The solution, says inventor Doug Selsam, is to think smaller: Capture more power with less material by putting 2, 10, someday dozens of smaller rotors on the same shaft linked to the same generator.

“The wind-turbine design out there right now is a thousand years old,” Selsam points out, as he lets one of his carved wooden blades speed to a blur in the makeshift wind tunnel he’s made of the alley behind his Fullerton, California, apartment. He brainstormed his multi-rotor approach in the early ’80s, in a fluid-dynamics class at the University of California at Irvine. “The textbook said, this single-rotor turbine design is the most power you can get. I knew then it wasn’t right. More rotors equals more power.”

How the Sky Serpent Works: Aligned at the optimal angle, each rotor receives its own wind, increasing efficiency.
Of course, more rotors also means more-complicated physics. The key to increasing efficiency is to make sure each rotor catches its own fresh flow of wind and not just the wake from the one next to it, as previous multi-rotor turbines have done. That requires figuring out the optimal angle for the shaft in relation to the wind and the ideal spacing between the rotors. The payoff is machines that use one tenth the blade material of today’s megaturbines yet produce the same wattage.

Selsam never did graduate from Irvine, but over the next couple decades he kept investigating novel wind designs, and by 1999, after an extended hiatus as a heavy-metal guitarist (he claims that the band Metallica stole its name from his group, Metallix), he turned to wind development full-time. In 2003, he landed a $75,000 grant from the California Energy Commission to develop a 3,000-watt turbine—his seven-rotor design met the challenge—and he has now sold more than 20 of his 2,000-watt dual-rotor turbines to homeowners. He’s built them all in his suburban garage.

“We’ve tested all kinds of wacko things that people think should make a lot of wind energy,” says Brent Scheibel, a former turbine tester for General Electric who now runs a wind-testing facility in Tehachapi, California. “The laws of physics take most of them out of the equation very early. Doug’s idea is one of the very, very few that I’ve seen that actually has a strong chance of making strides into the commercial world.”

Selsam says two rotors is just a start. Someday he sees his multi-rotor turbines stretching for miles across the sky. “We can go big,” he says, “and make turbines using this technique that are way more powerful than anything in GE’s wildest imagination.”

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19 Comments

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andrey_sichuga

from Indianapolis, IN

05/14/08 at 3:10 pm

i think that its a great idea, this way wind energy can be spread without the outrageous prices!!!!! ^__^

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redwarrior
05/14/08 at 7:43 pm

is the central shaft a static shape? or does it move in the wind like a kite?

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vector39
05/15/08 at 8:52 pm

the shaft can change shape as required- you could lift the far end with a balloon or mount it to a fixed pole- the shaft is flexi

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thatcher76
05/18/08 at 5:07 pm

I wonder if this thing could be improved by a better blade design as well:

http://www.whalepower.com/drupal/

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elovely
05/21/08 at 7:07 pm

I am a huge supporter of small wind, but I cannot think of many applicable situations for this design. This turbine seems to produce a pretty small amount of power for it's size and logistical concerns. A balloon holding up the other end of a string of turbines?? Good luck passing that through planning and zoning. I also believe that maintenence would be much more frequent with multiple turbines than some simpler designs. It's a cool idea, but before this guy spends much more time and money, he should pick up his guitar again.

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CalmLikeABomb
05/22/08 at 10:21 am

This is a great idea, and I had a thought about it,

If the blades were spinning, and these blades have the angle that pushes air out towards the preceeding turbine, then wouldn't it create some kind of perpetual motion system that would power every blade behind the first?

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topdog
05/25/08 at 1:18 pm

I think it's a great idea. I wonder how long the baloons can stay aloft. In my experience ballons usually lose their ability to stay airborne for more than 1 to 2 days. I also would like to know where I can get information on the units that are available for homeowners. My home never uses more than 2,000 (kWh) per month.

Thank you for your response in advance.

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miksimpson
05/29/08 at 5:21 am

Has anyone seen this website ,you might need to translate it first. http://www.membrana.ru/articles/inventions/2008/05/15/215200.html

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scooterbooter
05/29/08 at 8:59 pm

so if this man can have one than why cant every family in america get one so that we dont have to spend an outrageous amount of money for gas we could use wind power a source that would never run out and that mother nature creates naturally so why dont we all use wind power good job to the man that thought of this because he really opened my eyes and i think that we all need a good eye opener every once in a while

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scooterbooter
05/29/08 at 8:59 pm

so if this man can have one than why cant every family in america get one so that we dont have to spend an outrageous amount of money for gas we could use wind power a source that would never run out and that mother nature creates naturally so why don't we all use wind power good job to the man that thought of this because he really opened my eyes and i think that we all need a good eye opener every once in a while

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Cornfed
06/15/08 at 12:27 am

"Miles across the sky." You have to be kidding. I'm sure nobody will care that these fans are droning over their house from a distant neighbor while they can't have one because of interference problems. Back to the drawing board!

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murderdolls
08/02/08 at 7:08 pm

power i wonder what kind Yılan yağı kind of battery pack estetik not only is this just cool but all the amputies coming from war will now(soon) have a normal life. Kargo 1 out of 1 people found this comment helpful Cargo second is Lida power Tatil i wonder what kind of battery pack it requires to run one of those Lida

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Iggybuu
02/19/09 at 7:02 am

was wondering about hydro application

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murderdolls
04/13/09 at 5:32 pm

very goold..
very nice..
thank you..

thank you..

http://www.xfreepornmovies.com

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murderdolls
05/21/09 at 6:15 am

was wondering about hydro application

http://www.solaraluminyum.com/

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CommonSense
06/20/09 at 11:00 pm

Sorry to rain on anyone's parade but this design is a bit silly. How is filling up a balloon with helium (or Hydrogen or whatever lighter-than-air substitute) on a daily basis going to lower the cost of something and make it less complicated? For about $1,000 a 3kW wind turbine can be bought or built. So why have it so labor intensive? Also how is the high cost of a strong yet flexible drive tube/wire that this design requires supposed to make it cheaper and less complicated? Having multiple rotors isn't a bad idea it's just not a smart design configured as this one is shown. I've looked at the individual blade design as well and it looks like a lot of inefficient blades were substituted for one or even a couple of more efficient blades. Instead of using a modified automotive-style alternator/generator the R&D might be better focused in winding one that works better at the RPMs that are applicable to wind powered electrical generation.

It's just common sense, even when it's uncommon...

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gena
07/21/09 at 2:54 am

Capture more power with less material by putting 2, 10, someday dozens of smaller rotors http://www.crazypurchase.com

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tum3r
08/17/09 at 6:32 am

"Miles across the sky." You have to be kidding. I'm sure nobody will care that these fans are droning over their house from a distant neighbor while they can't have one because of interference problems. Back to the drawing board!

http://www.akasya-duragi.com/youtube-ktunnel

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bobo13
08/19/09 at 6:46 am

as wondering about hydro application

www.webressam.net



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